Random thought: To do G6 or above practical, it is a condition that you have G5 in theory, jazz or practical musicianship.
What if you had jumped straight in with G8 in one of these, rather than doing G5? The syllabus says G5 must have been passed, not 'G5 or above' must have been passed...
I'm guessing you can get an 'exemption' in the rare cases that someone takes e.g. G8 theory without having taken G5 theory/jazz/PM (and before they get to G6 practical...)
OK, so it's unlikely, that's what makes it a random thought rather than a serious enquiry!